Journal of Aquatic Plant Management 44: 115-121 (2006)
Giant salvinia (Salvinia molesta) is a noxious aquatic fern native to Southern Brazil that has threatened many freshwater ecosystems. Giant salvinia reproduces rapidly by fragmenting part of their stems to create a new plant. Its overgrowing has replaced native vegetation, altering the food web of the aquatic ecosystems, and also reduced dissolved oxygen levels, which eventually asphyxiates all aquatic life. It hinders irrigation, clogs waterways and promotes diseases in the stagnant waters the fern creates.
Daniel Flores and J.W. Carlson of the USDA introduced the salvinia weevil (Cyrtobagous salviniae) to control the fern. Herbicides usually exacerbate the situation or are not effective. The places where the researchers introduced the weevils have a significant decrease of the fern and an increase in dissolved oxygen levels. The giant salvinia population has remained constant and the weevils have shown to only consume the fern and nothing else. The authors say more research is needed, but biocontrol has shown to be an effective option.